The present invention relates to a magnetic disk drive and particularly to a load/unload mechanism for a magnetic head.
Along with the recent increased recording density of the magnetic disk drive, there is now a tendency to reduce the flying height of a magnetic head and to decrease the roughness of a magnetic disk surface. Therefore, according to the conventional contact start stop method wherein a magnetic head comes into contact with the surface of a magnetic disk when the rotation of the magnetic disk is stopped, the magnetic disk and the magnetic head are apt to adhere to each other, and as the case may be, the magnetic disk becomes difficult to start.
One of the methods for solving this technical problem is a method using a mechanism called a load/unload mechanism for loading and unloading a magnetic head with respect to a magnetic disk. This mechanism prevents mutual contact of the magnetic head and the magnetic disk when the rotation of the magnetic disk is stopped. According to this mechanism, when the rotation of the magnetic disk is stopped, a lift tab formed at a front end of a suspension is allowed to go up onto a ramp, whereby the magnetic head is brought into an unloaded state from the magnetic disk, while when the magnetic disk rotates, that is, during write or read of data, the magnetic head is moved (loaded) over the magnetic disk and is thus brought into a flying state.
However, the load/unload mechanism involves a problem in that a slide motion of the lift tab made of a metallic material causes a slide surface of the ramp made of a resin material to wear, thereby producing dust. The formation of dust must be prevented because it could cause a crash of the magnetic head.
According to a technique disclosed in Patent Literature 1 (Japanese Patent Laid-open No. 2002-367313), a porous member impregnated with lubricating oil is provided in at least part of a slide surface of a ramp to feed the lubricating oil to the slide surface of the ramp, thereby reducing sliding wear of the load/unload mechanism and preventing the formation of dust over a long period.
It has turned out that a frictional force acting between a lift tab and a ramp varies depending on the temperature of the lift tab and that of the ramp and exerts a great influence on the wear of a contact surface of the ramp. In a high temperature environment, the frictional force between the lift tab and the ramp is small in both loading and unloading operations and there scarcely occurs wear of the ramp caused by the repetition of loading and unloading operations. Conversely, in a low temperature environment, the frictional force between the lift tab and the ramp is large in both loading and unloading operations. This frictional force tends to become larger in proportion to falling temperature. Since the frictional force between the lift tab and the ramp thus becomes larger, when the lift tab is allowed to perform a motion of contact with the ramp, the wear of the ramp increases and the slide surface is scraped off. As a result, wear powder is produced, and once this wear powder drops onto the magnetic disk, the magnetic head when passing thereover treads on the wear powder. Consequently, the wear powder adheres to the magnetic disk or the magnetic head comes into contact with the magnetic disk, causing the occurrence of read and write errors of the magnetic head.